Hydrocarbon-oil conversion



Dec. 31, 1929. I c. J. PRATT 1,741,535

HYDROCARBON on. CONVERSION Filed July 8, 1926 Patented Dec. 31, 1929 UNITED STATES PATENT OFFICE CLIFTON J. PRATT, OF TULSA, OKLAHOMA, ASSIGNOR TO UNIVERSAL OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF SOUTH DAKOTA HYDROCABBON-OIL CONVERSION Application filed July 8, 1926. Serial No. 121,066.

This invention relates to improvements in hydrocarbon oil conversion and relates more particularly to a method whereby the charging stock is first subjected to a preliminary heating at a temperature regulated to avoid substantial cracking, this heated oil being then separated into its various fractions or cuts. These separated fractions or cuts are 'then separately subjected to independent conheavier fractions of the charging stock and underheating the lighter fractions, which of course results in inefficiency, loss and the formation of undesirable compounds in the oil.

By the present invention each fraction is independently subjected to the optimum temperature and pressure at which the most-citicient cracking will take place.

As a. feature of the invention, the separation of fractionation of the preliminarily heated but uncracked oil takes place in the dephlegmator, into which vapors from the in dependently heated cracking zones discharge. Thus there is a simultaneous fractionation of the charging stock and dephlegmation of the cracked vapors in the dephlegmator, the reflux distillate itself separating into cuts, which may be combined with the cuts from the uncracked charging stock.

The temperature maintained on the dephlegmator is regulated to control the amount of condensation taking'place in the dephlegmator in the usualmanner.

The singlefigure in the drawing is a diagrammatic side elev'ational view partly in vertical section illustrating and apparatus for carrying out the present invention.

Referring in detail to the drawing, 1 designates a charging stock line in which is interpos'ed a pump 2. This pump forces the charging stock through the line 1 into the heating coil 3 mounted in the turnace 4. The oil passing-through-the coil 3 will be subjected to a preliminary heating and a temperature short of the point where any substantial amount of cracking will take place and under super-atmospheric pressure if desired. The heated oil will discharge through the transfer line 5 controlled by valve 6 into the lower end of a dephlegmator or fractionating tower 7. This chamber 7 maybe provided with a plurality of spaced pans or collectors 8 disposed at varying heights throughout the tower 7. The major portion of the heated oil introduced into the tower 7 will vaporize and in its passage upwardly the major portion of these vapors will be con densed, it being obvious that this can be accomplished by suitable control of tempera- .ture. For instance, an auxiliary cooling medium may be introduced through the line 9 controlled by valve 10 if desired. The lighter fractions will collect in the upper pans 8, while the heavier fractions will condense in the lower pans. The fractions collecting in the spaced pans are separately withdrawn through the lines 11 controlled by valves 12 and in which lines may be interposed pumps 13 and passed to independent heatingcoils 14 disposed in separate furnaces, if desired, or as shown in the same furnace 4. These coils are shown as disposed in a vertical plane. It is obvious of course that this illustration is diagrammatic and that any arrangement for accomplishing the purpose may be utilized. The furnace may be heated by means of the burner 15, the gases of combustion passing upwardly in the first tube chamber, thence downwardly in the second tube chamber, and so on being deflected by the bafiles 16. It is to be noted that the heating coil 3 where the charging stock is subjected to the preliminary heating is located at a point most remote from burner 15. The waste gases of combustion may pass out through the stack 17.

It will be obvious from th foregoing description that each fractionis independently subjected to that temperature and pressure at which the most efficient cracking reaction will take place. More specifically, the lighter fractions collecting in the upper pans will be subjected tothe highest heat, while the heavier fractions collecting in the lower pans will be subjected to 'a lower heat. The proper temperature and pressure to be maintained on each independent fraction will be predetermined by analysis. Also it is to be understood that'there may be any number of pans in the dephlegmator for'the purpose of fractionation and that the length of the cracking coils 1 1 may vary to produce the desired result.

The heated fractions after being subjected to cracking temperature in the heating coils 14 may pass through the transfer lines 18 controlled by valve 19 to independent expansion chambers, or they may pass to a header 20 common to all of the lines 18 in which line 20 is interposed a valve 21. The header discharges the heated fractions into the expansion chamber 22, which is preferably an unheated, insulated, enlarged chamber provided with liquid residue draw-offs 23 controlled by valve 24 and with vapor discharge pipe 25 controlled by valve 26. Separation of vapors will take place in the expansion chamber 22 and carbon is allowed to accomulate. It is understood the chamber is provided with suitable manholes for the purpose of facilitating the removal of carbon.

The vapors passing through the line 25 discharge into the dephlegmator 7, where they are subjected to accurately regulated temperature conditions to cause regulated reflux condensation. Thus vapors remaining uncondensed after passage through the dephlegmator will pass out through the vapor outlet pipe 27 controlled by valve 28 and Wlll be condensed in condenser 29, the distillate being collected in the receiver 30, which may be provided with the usual pressure relief valve 31 and liquid draw-off valves 32.

The heavier liquid fractions of both the charging stock and the reflux condensate may be withdrawn from the dephlegmator 7 through the line 33 and by opening valve 34 may be cooled in the cooling coil 35 and collected in an obvious manner or, preferably, all or a portion of these heavy fractions Wlll .be diverted through the return line 36 controlled by valve 37 and in each may be interposed a pump 38, the pipe 36 merging with the charging stock line 1 prior to entering the tubes 3.

As illustrative of the temperatures and pressures which may be employed, the charging stock passing through the preliminary heating coil 3 may be subjected to a temperature of, say, 800 deg. F., more or less, under a pressure of. say, 100 to 17 5 pounds, more or less. This temperature and pressure ,will of course vary, but it is to be understood that the charging stock will be subjected to that temperature which will not produce substantial cracking. In the cracking coils 14, the lighter fractions will be subjected to a higher temperature, say, 87 5 to 900 deg. F., more or less, while the heavier fractions may be subjected to a temperature of 840 to 860 deg. F., more or less. Any desired pressure in excess of the presure maintained on tower 7 may be maintained on the heating coils and expansion chamber by means of the pumps 13. The flexibility of the process permits differential pressures to be maintained on various parts of the system by manipulation of valves and pumps in an obvious manner. It is to be understood that when a higher pressure is maintained on the heating coils 14 and expansion chamber 22, this is reduced by valve 26 to substantially the pressure maintained on dephlegmator 7.

It may be pointed out that it is preferable to subject the lighter fractions to a higher pressure as well as a higher temperature relative the heavier fractions.

Among the advantages of the foregoing process may be listed economy in operation due to conservation of heat, reduction'in loss normally resulting from cracking operations due to coke and non-condensable gas formation, decrease in amount of objectionable compounds formed in the oil and consequent decrease in subsequent refining treatment necessary for all the products of cracking. Primarily, as heretofore pointed out, these advantages are accomplished by subjecting the constituents of a charging stock to that temperature'and pressure at which most eflicient cracking reaction will take place.

I claim as my invention:

1. process of hydrocarbon oil conversion comprising subjecting the charging stock to a preliminary heating while maintaining same under a substantial non-cracking temperature and pressure, separating said heated charging stock into fractions, subjecting said separated fractions while isolated from each other to independent conditions of temperature and pressure, regulated to produce most efiicient cracking reaction of said separated fractions, permitting vaporization of said independently heated fractions to take place, separating said vapors and subjecting same to dephlegmation in the zone where fractionation of the charging stock takes place, and condensing the dephlegmated vapors.

2. A process of hydrocarbon oil conversion comprising subjecting the charging stock to non-cracking conditionsgof temperature to cause substantial vaporization, separating the constituents of said charging stockinto lighter and heavier fractions, simultaneously and separately subjecting the se arated fractions to independently controlle cracking temperature and pressure conditions, the

lighter'fractions being subjected to the higher cracking temperature and pressure conditions relative the heavier fractions, in permitting separation of vapors from said independently heated fractions, in introducing said vapors into the zone where fractionation of the charging stock takes place, and dephlegmating the vapors in said fractionating zone.

3. A process of hydrocarbon oil conversion comprising subjecting the charging stock to non-cracking conditions of temperature to cause substantial vaporization, separating the constituents of said charging stock into lighter and heavier fractions, simultaneously and separately subjecting the separated fractions to independently controlled cracking temperature and pressure conditions, the lighter fractions being subjected to the higher cracking temperature and pressure conditions relative the heavier fractions, in permitting separation of vapors from said independently heated fractions, in introducing said vapors into the zone where fractionating of the charging stock takes place and deplegmating the vapors in said fractionating zone, the reflux condensate separating in said fractionating zone into lighter and heavier fractions and combining respectively, with the fractions of the charging stock.

4. A process for cracking hydrocarbon oil comprising simultaneously advancing a plurality of independent streams of oil through independent heating coils positioned in successively hotter regions of a heating zone, permitting vaporizationof the heated oil constituents, introducing charging oil for the process to a fractionating zone, admitting vapors evolved from said heated oil constituents to said fractionating zone, supplying the lightest fraction from said fractionating zone to the heating coil positioned in the hottest region of said heating zone, supplying the relatively heavier fractions from said fractionating zone to the heating coils positioned in the regions of said heating zone of relatively lower temperature to supply the oil constituents flowing in said independent streams, and in maintaining superatmospheric pressure onthe oil constituents flowing through said heating zone.

5. A process for cracking hydrocarbon oil comprising fractionating the oil to be treated, independently passing the separate fractions of the oil while isolated from each other through separate regions of a heating zone, admitting the lightestfraction to the region of highest temperature and the heaviest fraction to the region of lowest temperature, permitting vaporization of the heated oil constituents and admitting the vapors to the zone of fractionation, and maintaining a superatmospheric pressure on the oil constituents flowing through said heating zone.

CLIFTON J. PRATT. 

